The invention relates to a slip-free pulley suitable for use as a rope sheave, or cable sheave or even as a belt pulley. Such pulleys or sheaves are either locked in a predetermined rotational direction and rotatable freely in the opposite direction or control means are provided which permit a manual control of the pulley so that it may rotate freely in both directions. The invention also relates to a method for operating such a slip-free pulley or sheave and an arrangement for performing such method.
Numerous rope and cable guide rollers are known in the art, which are locked in a defined rotational direction and freely rotatable in the opposite direction. Control means are commonly provided for such sheaves or pulleys to select the direction of rotation in which the pulley shall be freely rotatable. Such additional control devices do not permit the control by one hand only. In addition, prior art devices are not readily suitable for remote control. Thus, in known pulleys, it cannot be avoided that in the arrested position of the pulley, the rope slides over the locked roller with substantial so called slip, whereby the rope is subject to substantial wear and tear.
German Patent Publication No. 22,32,740 described a free wheeling pawl clutch, whereby the pawls are supported without bolts in a pawl carrier. The pawl carrier is cylindrical and has a flattened portion in the range of each pawl. Cylindrical recesses are arranged in the flattened portion with their axes in parallel to each other to receive the pawl foot. These recesses are set back to such an extent relative to the cylindrical outer contour of the pawl carrier, that in the withdrawn position of the pawls, the latter do not reach into the range of the gear teeth of the ring which cooperates with the pawls. This known coupling according to German Patent Publication No. 22,32,740 is also locked in one rotational direction and does not permit the release or unlocking, if necessary.